Hardware uniqueness

From OLPC

What makes this system unique?

What are the features one would want for school-aged children, grades K–12? A large fraction of such children are in parts of the developing world where electricity is not available at home, or often even at school, so for many children, a low power consumption, potentially a human-powered computer is a necessity, not a convenience. Teaching may not even be inside, and certainly when children are at home, they often will not be inside where conventional LCD screens are usable. Children usually walk to and from school every day; weather is unpredictable, rain, dirt and dust are commonplace. And cost is a major consideration, if we are to bring computers and their great power to help children learn to children everywhere.

The OLPC design reflects these realities, thanks to the work of our design team, which includes OLPC staff, Quanta Computer, the Fuse Project, Design Continuum, members of the MIT Media Lab and other colleagues and friends. It also reflects a great focus on what can and should be done to help bring the children the best possible learning tool, and reflects decades of field experience of children using computers in the developing world. Our thanks to them all.

It is sized for a child, who, due to their size, will be closer to the screen than an adult with a conventional laptop. The system is much lighter than a conventional machine, (somewhere less than 1.5KG), and its industrial design is quite different than a commercial "black/grey/white" laptop.

It has a rugged handle for carrying easily, sized for children. This reflects the needs of children walking to and from school or other activities.

"Transformer" screen hinge: E-Book Mode for convenient reading and a conventional laptop mode. It folds over into a "ebook", about the size of a conventional book, with buttons exposed for controlling viewer applications (or for use with games).

The screen can be "on" while the CPU and most of the motherboard is suspended and powered down, while the screen is read or the machine otherwise idle, allowing for major power savings in most common usage modes, such as reading a book.

The screen refresh rate can be varied. When applications are not changing the screen, we can reduce the refresh rate of the LCD to conserve power.

Wireless mesh: Child-child sharing! OLPC Laptops are full-time wireless routers. Mesh networking reduces the need for dedicated infrastructure (e.g. access points and/or cabling), and extends greatly the areas in which machines may be connected to each other and/or to the internet.

The wireless antennae are diversity antennae, and rotate upward using a rugged dual moulded nylon plastic design. When used rotated above the LCD, the antennae work significantly better than conventional built in antennae in existing systems or in Cardbus cards. This significantly increases the area each machine can cover in the mesh, and generally increases network performance. When closed, the antennae cover the audio and USB connectors to help keep dirt out of the connectors (as mentioned above, the case carefully molds around the connectors, both to increase ruggedness and to help keep dirt and water out). Great care has been taken in the RF design, and early measurements show a lower noise level than seen by Marvell on any other design of theirs. We expect that the 802.11 networking in this system will be substantially better than a conventional system.

The Marvell wireless chip can forward packets in the mesh network, with the CPU suspended, and the CPU may resume if explicitly addressed. Since the mesh network is so important, we want laptops to be able to participate in the mesh to keep forwarding packets when need be as efficiently as possible, and by suspending the processor we can increase the running time of the wireless by a factor of 3-4. If this were not possible, children might need to disable wireless to preserve battery charge; by doing so, the mesh would be much less effective.

The machine is rugged. The most common failures of laptops are disk drives, fans, fluorescent back lights, power connectors, other connectors, and contamination of keyboards. Our machine uses flash, eliminating a disk, has no need for a fan, uses a rugged LED backlight rather than a fluorescent light, and uses a sealed rubber keyboard. It uses 2mm thick plastic, where a typical system might use 1.3mm. External connectors are carefully molded into the plastic for greater strength. The power connector is carefully chosen to be much more durable than usual, and again, the case is moulded carefully around it for greater strength. There are extremely few connectors in the machine, primarily just connecting the keyboard assembly to the motherboard (which is behind the LCD display). This eliminates most of the cables and connectors you will find in most laptops. We will be testing 500 systems to destruction this fall to identify anything we can do to further increase its ruggedness. There are internal bumpers to protect the display, and we are investigating external bumpers on the outside of the case for additional shock protection.

Additionally, the design allows us to directly connect the video output of the DCON chip to the LCD, enabling lower power drive of the screen.

With these special power savings features, average power consumption, is expected to be low enough (in the neighborhood of 1-1.5 watts in many usage scenarios) that if a child needs to generate power for their laptop, they will get a good ratio of "work" to "learn". A small child can generate at best 5-10 watts; a larger child somewhat more. In contrast, conventional laptops often consume 20 watts or more, even when idle.

The industrial design includes a small lip to help seal the edge of the machine when closed. While not water-proof, we expect a machine in a child's backpack or hands in a rainstorm should not have problems with water.

The keyboard is a rubber membrane keyboard, with quite nice feel (and we continue to work on further improvements on it). This makes the keyboard much more resiliant against both water and dirt, and allows us to seal the keyboard in the base of the machine. The keyboard is connected via a PS/2 interface to save power. Smaller key pitch for smaller hands. A lighter 40 gram touch than normal keyboards.

Dual cursor control pads (w/Enter keys)

Internal microphone, plus a mic-in jack. Unique “sensor input” mode. The audio codec can be used in a mode where direct voltage measurements can be taken, enabling children to learn about temperature, voltage, and many other physical phenomena with cheap sensors without requiring any external adaptors. The educational possibilities are limited only by your imagination.

Stereo audio with internal stereo speakers; Stereo Line-out jack

There are three USB2 connectors, allowing for many expansion possibilities.

The power supply is tolerant of almost any voltage you might have at hand for charging, either from a human powered generator or a car or truck battery; accidental reversal of polarity will not damage the machine.

NiMH batteries are chosen to enable high charging efficiency from a generator (LiION batteries require very close control of charging voltages, so any higher voltage would have to be clamped and power wasted). Additionally, NiMH batteries have no safety problems (LiION batteries, when they fail, can fail by burning at extremely high temperature). And LiION batteries should be recycled carefully. NiMH batteries pose no environmental concerns.

Long battery life => more useful. Under typical use, the computer should last the entire school day without requiring charging. Avoiding disruption in class rooms, and/or the need for wiring (or use of generators)in the class room for power is very important.

Removable battery packs, that are much lower cost than conventional LiION battery packs. This enables easy swapping of batteries so that one set might charge while another is in use.

From the above, you can see that this is a novel system carefully designed to solve the challenges outlined above, and not a typical "laptop" in almost any dimension you care to name.

Where's the Crank? (you are asking...) Human power is still a major program priority! Inside the laptop isn’t always optimal as human power is not always required. Human power stresses components. The crank is great symbolically, but not the most efficient for actual generation. We are performing human motion studies: legs are stronger than arms, but arms may be free while walking to school. AC Adapters are already located on the ground/ and floor. Several types of generators are under development, including one integrated with AC Adapter. More freedom of motion will allow for optimum power generation.